Technology Overview

GSM (Global System for Mobile Communications) networks have been deployed worldwide as second-generation mobile communications systems. GSM originally was developed to transmit voice, but is also able to transmit data with a max. load of 9.6 kbit/s in the downlink and uplink. With the technical interim solution HSCSD, the max. data rate was increased to 43.2 kbit/s in the downlink and 14.4 kbit/s in the uplink.

In Europe, GSM networks operate in the 900 MHz and 1800 MHz bands, while the USA and Canada use the 850 MHz and 1900 MHz bands. In addition, the 400 MHz and 450 MHz bands are becoming more and more popular in rural areas due to reduced requirements for base station density.

For voice transmission, voice codecs are used: "full rate" with 13 kbit/s to digitize a 3.1 kHz audio signal and "half rate" with 6 kbit/s digitization.

Packet data capabilities were added in the Release ’97 version of the GSM standard by means of GPRS (General Packet Radio Services). GPRS is a data service that is available to users of GSM and IS-136 handsets. GPRS can be used for all data services such as Internet browsing, WAP access, SMS, and MMS. In comparison to GSM, GPRS is packet-switched; in terms of multiple users, it shares the same transmission channel only when data must be sent. The max. data rate in GPRS for class 10 is 60.0 kbit/s in the downlink and 40 kbit/s in the uplink.

To increase the data transmission rate and to improve network capacity, EDGE (Enhanced Data for GSM Evolution) was introduced in Release ’98. With EDGE, a new modulation scheme is applied: 8-PSK (phase shift keying), i.e. three bits per RF modulated symbol as opposed to the original one bit per symbol in GPRS. This technology change triples the effective data rate. EDGE carries a peak date rate of 384 kbit/s in the downlink. The average data rate in commercially operated networks is in the range of 200 kbit/s. EGPRS is a superset expression comprising EDGE and GPRS.

EDGE evolution contains a set of features specified in Release 7. The primary motivation for enhancing EDGE is to ensure the future competitiveness of the dominant second-generation technology and specifically to provide service continuity across the various radio technologies (GERAN, UTRAN) supported by core network evolution, e.g. IMS. The improvements include DL dual carrier operation, higher order modulation (16QAM, 32QAM) in combination with an optional higher symbol rate and turbo coding, latency improvements, and the use of RX diversity at the mobile station. Depending on the features applied, peak data rates of up to 1 Mbit/s will be achieved.

Rohde & Schwarz provides a complete product portfolio for GSM/GPRS/EDGE: digital standards on general-purpose equipment such as the R&S®SMU and the R&S®FSQ; dedicated communications testers, e.g. the R&S®CMU200/300; protocol testers such as the R&S®CRTU-G; and complete conformance test systems, e.g. the R&S®TS8950G. We have been offering products since the early introduction of GSM into the market and thus understand all aspects of implementing the latest developments in this technology.

Deployment Scenario

GSM (EDGE) is the most popular mobile phone standard with rollouts across 213 (149) countries worldwide, serving more than 2.5 billion users. GPRS, which only requires a software upgrade in the base station, has also been rolled out worldwide. EDGE, which was initially introduced in North America, has also been deployed in Europe and Asia.

Key Parameters

Standardization

In 1989, the GSM standard was defined by the Groupe Speciale Mobile and became an internationally accepted digital cellular telephony standard. GSM was later transferred to the ETSI technical committee, which continued to define the GSM standards. Today, GSM and EDGE are being specified in 3GPP (3rd Generation Partnership Project) and coordinated in TSG GERAN. The following link provides access to TSG GERAN specifications: http://www.3gpp.org/ftp/specs